It has become possible to produce monoclonal antibodies to T cells, B cells and their individual subsets of human lymphocytes by recently developed cell technological procedures, and the individual cell groups have been gradually clarified [Reinherz, E. L. et al: Cell 19, 821 (1980), Foon, K. A. et al: Blood 60, 1 (1982)].
That is, functional cell subsets of human lymphocytes have been much clarified by using monoclonal antibodies recognizing these subsets, and their abnormalities in various diseases have been gradually clarified.